The disclosure relates to a linear drive, in particular for a piston pump, having a first electromagnetic drive device, having a second electromagnetic drive device and having a drive piston which can be moved in an axial direction by means of the drive devices. The disclosure also relates to a piston pump arrangement.
The linear drive has the two electromagnetic drive devices and the drive piston, which can be moved in an axial direction by means of the drive devices. Here, a movement of the drive piston in a first direction can be effected by means of the first electromagnetic drive device, and a movement of the drive piston in a second direction opposite to the first direction can be effected by means of the second electromagnetic drive device, by virtue of the respective drive device generating a magnetic field. The linear drive can particularly advantageously be used as a drive for a piston pump.
Known from the prior art is, for example, DE 30 33 684 A1 which describes a piston pump with electromagnetic drive. Here, the piston of the piston pump is in the form of a drilled-through cylinder composed of ferromagnetic material of high remanence and high coercive force, and is permanently axially magnetized. The piston, in a cylinder liner which is composed of non-magnetic material, moves back and forth between the poles of two coaxially configured electromagnets under the influence of an excitation current. The magnetic circuit is closed in each case by means of a common force-guiding piece directed radially toward the center of the piston, wherein preferably, a valve situated in the axial longitudinal bore of the piston serves to ensure a unidirectional flow.
The use of an electromagnetic linear drive of said type is however often possible only with great outlay and with high material costs, in particular owing to a commonly required high-energy permanent magnet ring, because firstly the force and/or the maximum attainable stroke frequency of the linear drive are not sufficient, and secondly the linear drive exhibits greater power consumption than a rotating electric motor which actuates the pump piston eccentrically. This is a problem in particular when the linear drive is used for a piston pump in a vehicle control system, in particular in a driver assistance system. In the latter, use is thus commonly made of piston pumps which have the above-described rotating electric motor which actuates the pump piston eccentrically by means of an eccentric. This means, however, that the volume flow of the fluid delivered by means of the piston pump can be adjusted only by means of the rotational speed of the electric motor, that is to say by means of the frequency of the eccentric actuation.